A holographic recording medium on which data are recorded holographically has been invented (e.g. see JP-A-2004-029476). The holographic recording medium is a photosensitive recording medium in which holographic recording layers each made of photosensitive material are provided on a disc-shaped support. Data are multiplexedly recorded as interference fringes of laser light, so that a larger data recording capacity than that of a DVD which is a recording medium heretofore widespread can be obtained. Exposure of the holographic recording layers to light or deposition of dust on the holographic recording layers exerts a bad influence on the performance of the holographic recording medium. For this reason, the holographic recording medium is dealt with in the condition that the holographic recording medium is stored in a cartridge having a light-shielding function and a dustproof function (e.g. see JP-A-2003-317422 (corresponding to US 2003/0198177 A1)).
In the invention described in JP-A-2004-029476, the holographic recording medium is stored in a cartridge similar to the cartridge of a DVD-RAM. The cartridge is made of a material low in transmittance of light rays in a wavelength range exerting influence on the holographic recording layers. On the other hand, in the invention described in JP-A-2003-317422 (corresponding to US 2003/0198177 A1), a cartridge is made of a material capable of blocking light with a color sensitive to the holographic recording layers, and a sponge-like light-shield material is stuck to a mating portion of a movable portion for exposing the holographic recording medium to the outside.